In the manufacture of a semiconductor device, a thermal CVD (Chemical Vapor Deposition) apparatus, a photo CVD apparatus, or a plasma CVD apparatus is used in a method for forming a highly functional film (such as a highly conductive film with a low impedance that corresponds to a circuit wiring in a semiconductor chip, a highly magnetic film having a function as a wiring coil of a circuit or a function as a magnet in a semiconductor chip, a highly dielectric film having a function as a capacitor of a circuit in a semiconductor chip, and a highly insulative film formed by oxidation or nitriding and having a highly insulating function that causes a less amount of electrical leakage current in a semiconductor chip). Particularly, the plasma CVD apparatus is often used. For example, as compared with the thermal and photo CVD apparatuses, the plasma CVD apparatus is advantageous in that the temperature of film formation can be lowered, the speed of film formation is higher, and a film formation process can be performed in a short time.
For example, to form a gate insulating film such as a nitride film (for example SiON or HfSiON) or an oxide film (SiO2, HfO2) on a semiconductor substrate, the following technique that uses the plasma CVD apparatus is generally adopted.
Thus, a gas of NH3 (ammonia), N2, O2, O3 (ozone), or the like, and a precursor gas of silicon or a hafnium material are directly supplied to a film formation process chamber of a CVD apparatus, for example. Thereby, a chemical reaction caused by heat, a catalyst, or the like, is promoted, and the precursor gas is dissociated. Metal particles resulting from the dissociated precursor are oxidized or nitrided by the added gas of NH3 (ammonia), N2, O2, O3 (ozone), or the like, and are deposited on a semiconductor wafer that is a processing object. After the deposition, a heat treatment is performed so that a crystal growth occurs. Through the above-described steps, a highly functional film is formed. Accordingly, in the CVD apparatus, high-frequency plasma or microwave plasma is directly generated in the process chamber. Under a state where a wafer substrate is exposed to a radical gas and plasma ions or electrons having a high energy, a highly functional film such as a nitride film or an oxide film is formed on the wafer substrate.
For example, Patent Document 1 may be mentioned as a related art document that discloses a configuration of the plasma CVD apparatus.
In the film formation process within the plasma CVD apparatus, the wafer substrate is directly exposed to plasma, as described above. Therefore, a problem always occurs that the wafer substrate is largely damaged by plasma (ions or electrons) to cause a deterioration in the performance of a semiconductor function.
In contrast, in the film formation process using the thermal and photo CVD apparatuses, the wafer substrate is not damaged by plasma (ions or electrons), so that a highly functional film such as a nitride film or an oxide film is formed with a high quality. However, such a film formation process involves a problem that it is difficult to provide a nitrogen radical gas source or an oxygen radical source with a high concentration and a large amount, and consequently a very long time is required for the film formation.
In the recent thermal and photo CVD apparatuses, a high-concentration NH3 or O3 gas, which is readily dissociated by radiation of heat or light, is used as the source gas, and a thermal catalyst is provided in a CVD chamber. Accordingly, in the thermal and photo CVD apparatuses, a catalytic action promotes dissociation of the gas in the chamber, and a time period for formation of the highly functional film such as a nitride film or an oxide film can be shortened. However, this method faces difficulties in considerably improving the time period for film formation.
Therefore, as an apparatus that can reduce damages to the wafer substrate caused by plasma and that can shorten a time period for the film formation, a film formation processing apparatus of remote plasma type may be mentioned (for example, see Patent Document 2).
In a technique of the Patent Document 2, a plasma generation region and an object processing region are separated from each other by a partition (plasma confinement electrode). More specifically, in the technique according to the Patent Document 2, the plasma confinement electrode is provided between a high-frequency application electrode and a counter electrode on which a wafer substrate is placed, to thereby allow only neutral activated species to be supplied onto the wafer substrate.
Recently, in addition to the application for forming a functional film of a semiconductor, an application using a plasma excitation gas (an active gas, a radical gas) caused by discharge have arisen. One of previous examples thereof is a conventional technique (for example, Patent Document 3) relating to a photocatalyst material generation apparatus using discharge, in which dielectric barrier discharge (silent discharge or creeping discharge) is caused in a discharge gap and fine particles of a metal are put into the dielectric barrier discharge to thereby modify surfaces of the fine particles of the metal into a metal oxide, and a metal oxide material obtained as a result of the surface modification serves as a photocatalyst material.
In the technique according to the Patent Document 3, a high-voltage electrode and a low-voltage electrode are arranged opposed to each other with interposition of a dielectric and a discharge space (such a configuration including a pair of electrodes, a dielectric, and a discharge space will be referred to as an electrode cell).
An AC voltage is applied to the electrode cell, so that dielectric barrier discharge (high-field intermittent discharge plasma) is caused in the discharge space. A source gas containing an oxygen gas and an ozone gas, which is obtained by mixing a powdered metal into oxygen, is supplied to the discharge space where the intermittent discharge plasma is occurring. This generates activated oxygen radical (O atom radical) in the discharge space, and a discharge chemical reaction occurs between the activated oxygen radical (O atom radical) and the powdered metal. The discharge chemical reaction causes the powdered metal to be modified into metal oxide powder. Moreover, due to the discharge chemical reaction in imbalanced discharge plasma generated by the dielectric barrier discharge, fine particles of a photocatalyst material having a good photocatalyst function is generated.